Various apparatus and methods are now used for the purpose of vacuum sealing plastic bags to protect perishables, such as foodstuffs, and other products against oxidation. Conventional apparatus are generally expensive to manufacture, complex in construction and cumbersome to operate. One conventional type of vacuum sealing system, primarily used for commercial packaging purposes, includes a vacuum chamber in which the entire packaged product is placed, along with heat sealers and attendant components of the system.
Another type of conventional vacuum sealing system uses a vacuum nozzle that is inserted within a plastic bag for evacuation purposes. Although adaptable for low-volume home use, the latter type of system is cumbersome to use and normally requires a liquid separator or filter to prevent liquids or powders, retained within the bag, from being drawn into a vacuum pump connected to the nozzle. Further, the heat sealer employed therein must be closely calibrated and synchronized with the positioning and withdrawal of the vacuum nozzle from the bag.
Still another type of conventional vacuum sealing system places a portion of a bag, containing a product to be packaged, in a first vacuum chamber and extends an open end or neck of the bag into a second vacuum chamber. The first vacuum chamber is then evacuated to expand the neck of the bag to isolate the chambers from each other whereafter a vacuum is drawn in the second vacuum chamber to evacuate the bag. Thus, isolation of the two chambers from each other, during evacuation of the second vacuum chamber, is critically dependent on the physical properties composing the neck of the bag (which is intended to form a static seal between the two chambers) and very close synchronization and calibration of the evacuation and sealing procedures and controls therefor. A vacuum sealing system of this type is disclosed in U.S. Pat. No. 3,928,938, for example.
U.S. Pat. No. 2,778,171 discloses another vacuum sealing system which, to applicant's knowledge, has not been commercialized. In particular, the open end of a plastic bag is placed between a pair of jaws (FIGS. 14-17) or between a lower jaw and a flexible sheet (FIGS. 18-20) to evacuate the bag which is then heat sealed. An inner surface of the bag has protuberances (FIGS. 1-4) formed on it which make point contact with an opposed surface of the bag to define air exhaust passages during evacuation.